I'm being cynical, so warning for that.
A story about two girls being fine with their "disgusting" hobbies ended up with one of them basically sanitizing said hobby, and even having a typical manga ending of "doing my hobby... competitively!!" which is, y'know, very japanese but it definitely seems to bypass any emotional motivations she might have had for that. (a hobby that began as a very personal thing...Do you really want to put it out there for anyone to see, and if so, why? Questions like this weren't even considered.)
This story had a girl with a repulsion for sex that was so bad she spent almost the entirety of the manga convinced she was in the right for hurting a girl who loved her. In the end, she explains her trauma in the most matter-of-fact way, just telling us what we already know, almost like instead of processing it she's just... giving us the notes the mangaka had written about her when she had to sent this story to her editor's. Again, we aren't really privy to the emotional developments that led to her being okay with sex all of the sudden.
This story spent most of its runtime developing the relationship of two people, Remu and Azuki, who were way too compatible. They had sexually intimate scenes together. In the end, Azuki ends up with her ex-gf. Why? Because it is much more neat that way. LIke this, no one has to face any "awkwardness": Meguru doesn't have to face her little sister be with the person who she fumbled. Azuki doesn't have to grow out of her unhealthy attachment to a girl who she doesn't even know that well, and Remu... well, she was already a paper-thin character, so this way the story doesn't have to consider her inner world as a thing that might exist.
Look, I'm a self-described degenerate. Not in the sense that I'm any more of a pervert than anyone else, but moreso that I embrace that perversion. "Perversion", "deviation", "degeneration" these are just words that point to being outside the norm in ways that are socially damning, but I think people having such fixations is wonderful, since it allows for people to think and experience life in novel ways (not to mention, these are words usually used by fascist and authoritarian regimes to designate those they don't like). There's a quote out there by famous anime director Tomino Yoshiyuki about how you can only be a good animator if you're a pervert, and I agree; I think that goes for making manga, too. And this author isn't a pervert at all. I just think they liked the aesthetics of perversion. It managed to completely fool me into thinking that this would be an interesting work, but I am saddened by the flaccidity in which it has decided to finish. It definitely lacked the courage to engorge itself and revel in its perverted potential.
All in all, this series was a dissapointment and I hate that I wasted time of my life following it.
You articulated this well. I think she sheer amount of time spent with Azuki and Remu makes this ending feel weird. The idea that Azuki would get over Meguru with this new relationship makes sense. The manga also made it pretty clear Remu was catching feelings for Azuki and they just…kinda dropped it.